Solid state light sources may be utilized to provide colored (e.g., non-white) or white light (e.g., perceived as being white or near-white). A solid state lighting device may include, for example, at least one organic or inorganic light emitting diode (“LED”) or a laser. White solid state emitters have been investigated as potential replacements for white incandescent or fluorescent lamps due to reasons including substantially increased efficiency and longevity. Longevity of solid state emitters is of particular benefit in environments where access is difficult and/or where change-out costs are extremely high.
Because light that is perceived as white is necessarily a blend of light of two or more colors (or wavelengths), and light emitting diodes are inherently narrow-band emitters, no single light emitting diode junction has been developed that can produce white light. A representative example of a white LED lamp includes a blue LED chip (e.g., made of InGaN and/or GaN), arranged to stimulate a phosphor one or more phosphors (e.g., commonly yellow phosphors such as YAG:Ce or BOSE). A portion of the emissions of the blue LED chip pass through the phosphor, while another portion of such emissions is absorbed by the phosphor, which becomes excited and emits yellow emissions. The resulting mixture of blue and yellow light (sometimes termed ‘blue shifted yellow’ or ‘BSY’ light) may be perceived as cool white light. Various methods exist to enhance cool white light to increase its warmth, including supplementation with a red LEDs or red phosphor. Additional or different supplemental LEDs and/or phosphors (e.g., of other colors) may be used.
Various methods exist for arranging lumiphoric materials (e.g., phosphors) to be stimulated by solid state emitters. According to one method, one or more lumiphoric materials are coated directly on a surface of a solid state emitter chip, which may be incorporated into a lighting device. A solid state emitter chip LED can be coated and fabricated using many different methods, with one suitable method being described in U.S. Patent Application Publication No. 2008/0173884 to Chitnis et al. entitled “Wafer Level Phosphor Coating Method and Devices Fabricated Utilizing Method. Alternatively a LED may be coated using other methods such as electrophoretic deposition, with a suitable method disclosed in U.S. Patent Application Publication No. 2007/0158668 to Tarsa et al. The foregoing published applications are commonly assigned to the owner of the present application and are hereby incorporated by reference as if set forth fully herein. According to another method, a solid state emitter chip may be mounted to a mounting element (e.g., a flat substrate, a recessed surface bounded by a reflector, or other configuration) and one or more lumiphoric materials may be combined with a binder (e.g., epoxy or silicone) and deposited in one or more layers over the previously-mounted solid state emitter chip. In yet another method, one or more lumiphoric materials may be associated with an optical element such as a lens that is positioned on or over a solid state emitter chip.
Various solid state lighting devices including multiple discrete layers or regions of lumiphoric materials are disclosed in U.S. Patent Application Publication No. 2009/0039375 A1 to LeToquin, et al. and U.S. Pat. No. 7,709,853 to Medendorp, Jr., which are commonly assigned to the owner of the present application and are hereby incorporated by reference as if set forth fully herein.
Although lighting devices including multiple discrete lumiphoric material layers or regions according to certain configurations are known, various improvements to the foregoing configurations would be desirable. It would be desirable to enhance adhesion between such layers or regions. It would also be desirable to facilitate greater control of optical properties (including, but not limited, focus and/or directionality) of lighting devices including lumiphoric materials. It would further be desirable to enhance color mixing of, and/or increase light extraction from, lighting device including lumiphoric materials. Various embodiments as disclosed herein address or more of the foregoing concerns.